Semiconductor integrated circuits (ICs) are typically mounted in or on a printed circuit board (PCB) as part of a packing process. For electrical ICs, in one approach individual metal wires are used to make electrical connections between first metal pads on the IC and second metal pads on the PCB as part of a process referred to in the art as “wire bonding.”
The need for high-bandwidth communication with electrical ICs has prompted the addition of optical waveguide connections between optical+electrical ICs (“OE-ICs”) and OE-PCBs that have both optical and electrical functionality and optical and electrical connection locations. Like the wire bonding of electrical ICs, optical wire bonding along with the electrical wire bonding is performed between OE-ICs and OE-PCBs. The optical wire bonding can be carried out for example using flyover optical fibers routed above the OE-PCB surface. In this case, the OE-IC packing must incorporate optical connector hardware (e.g., precision fiber connector alignment features, such as alignment pins and holes) to support pluggable optical jumper cables. This increases the packaging cost and complexity of the OE-ICs.
More recently, ball grid arrays of solder balls are being used to form electrical connections between electronic PCBs and electronic ICs in a “flip chip” configuration. Unfortunately, there is no viable optical equivalent of the ball grid array for use with OE-PCBs and OE-ICs. Other approaches for making the optical interconnections in a flip chip configuration include using individual optical fibers or micro-optics to define free-space optical paths. Unfortunately, these approaches suffer from serious alignment issues that make them relatively low yield and difficult to implement.